The present investigation deals with-the effect of surface mass flux on mixed convective flow past a heated vertical flat permeable plate with thermophoresis. A nonuniform surface mass flux through the permeable surface has been considered. The governing equations, reduced to local nonsimilarity boundary layer equations using suitable transformations, have been integrated employing an implicit finite difference method together with the Keller-box technique (Keller [Annual Rev. Fluid Mech. 10 (1978) 417-433]). Perturbation techniques are employed to obtain the solutions near the leading edge as well as far from it. The perturbation solutions are compared with the finite difference solutions and found to be in excellent agreement. For fluids having the Prandtl number Pr = 0.7 and Schmidt number Sc = 10.0, numerical values of physical quantities, such as the local skin-friction coefficient, the local Nusselt number and the local Stanton number, are presented in tabular form for different values of the thermophoretic parameter tau against the local buoyancy parameter xi for impermeable surfaces. Profiles of the dimensionless velocity, temperature and concentration distributions as well as the local skin-friction coefficient, local Nusselt number and the local Stanton number are shown graphically for various values of suction parameter, f(w), Schmidt number, Sc and the thermophoretic parameter tau. (C) 2003 Editions scientifiques et medicales Elsevier SAS. All rights reserved.